Bar code label

ABSTRACT

A bar code label has a base in which recesses are engraved each in a predetermined shape corresponding to the information to be recorded. The base is protected by a coating of a non-magnetic material which prevents corrosion of the bar code label and allows it to be easily cleaned. Information can be accurately recorded and preserved on the bar code label for a long period of time as a result of the protective coating. Additionally, a bar code reader is used to easily and accurately read the bar code label. The bar code reader incorporates a magnetic sensor to detect a magnetic field charge.

This is a division of aplication Ser. No. 07/647,619, filed Jan. 28,1991.

FIELD OF THE INVENTION

The present invention relates to a bar code label in which informationon each of various goods, outdoor installations, individuals or the likeis recorded as engraving in the form of characters and bar codes. Theinvention also relates to readers for the bar code labels.

DESCRIPTION OF THE PRIOR ART

Bar code labels are well known and widely used attached on the surfaceof a box or package in which goods or a delivery is packed.

The bar code label carries a variety of information coded in the form ofbars different in width from one another. The information is used for ahigher efficiency and less labor in sales calculation, inventory controlor sorting.

Generally, such bar code is black bars printed on the white surface of abar code label.

If the label surface is stained with an oil or dirt or if the blacknessof the coded bars fades, the information recorded in the bar code labelcannot possibly be read positively and accurately. Particularly, thereis a problem in reading the bar code label outdoors.

Recently, a magnetic bar code reading system has been proposed which canbe used in any environment. In this system, engraved recesses(characters and bar codes) 202, 202', 203, . . . are made, as shown inFIG. 1, on a bar code label 201 made of a metal such as iron and therecesses are magnetically detected by means of a ferromagneticresistance device (referred to as "MR device" hereinafter) and apermanent magnet. More particularly, the head at the bottom of a mainbody 204 in which the MR device and permanent magnet are integrallyincorporated is swept across the engraved bar code label 201 to read therecess pattern consisting of the recesses 202, 202', 203, . . . . Theprinciple of this bar code reading will be discussed below:

When the head is placed on the engraved bar code label 201, the engravedrecesses 202, 202', 203, . . . are magnetized by the DC magnetic fieldformed by the permanent magnet. The magnetic field formed by thesemagnetized recesses causes the magnetic flux distribution over therecesses to change and these changes of the magnetic flux distributionresult in resistance changes of the MR device. The resistance changesare passed to the signal processing circuit provided in the head of themain body 204 in which they are converted into binary-coded (0 or 1)signals corresponding to the code represented by the recess pattern.This binary-coded signal is supplied to the decoder for recognition ofthe bar code pattern.

The conventional head of the magnetic bar code reader operating on theabove-mentioned principle has a tip of which the structure will bediscussed below with reference to FIG. 2. Namely, for an electricalconnection between an input wire of an MR device 206 made on a printedcircuit board 205 through a well-known IC manufacturing process and anexternal lead wire 207 through which a current is supplied to detect amagnetic field change as a voltage, the circuit board 205 is connectedto an electrode 209 by means of a bonding wire 208 and the external leadwire 207 is spot-joined to the electrode 209 by means of a solder joint210. The electrode 209 and circuit board 205 are attached to an internalsubstrate 211. Further, the internal substrate 211 and electrode 209 areattached to a head frame 212 and sealed from below with a coating film213. A permanent magnet 214 provided for exciting is attached to theinternal substrate 211 and sealed with a coating film 215.

As the conventional sensor of the magnetic bar code reader operating onthe above-mentioned principle, a generally square MR device is used asshown in FIG. 3. As seen, a magnetic resistance film 217 formed on acircuit board 216 made of, for example, a glass is provided in such astructure that it is folded back in parallel to the lateral side of thecircuit board 216. For a high magnetic sensitivity, a plurality of suchmagnetic resistance films cascade-connected is provided. Usually, thenumber of the magnetic resistance films thus provided is such that thewhole resistance will be on the order of several kiloohms. Furthermore,a current-supplying electrode 218 is provided on either end of themagnetic resistance film 217 in such a manner that an ohmic contact canbe assured. For a higher yield of manufacture with a reduced IC area,these patterns are so set as to form together a generally square shapein many cases.

In a magnetic bar code reader, the above-mentioned MR device is inclinedmore than 30 deg. with respect to bar code recesses 219 and a permanentmagnet 220 which applies a biasing magnetic field is provided on the MRdevice to make a head 221 which will be swept across recesses 223,engraved in the form of bar code in an iron sheet 222, in a directionperpendicular to the length of the engraved recesses 223, therebyreading the bar code.

A bar code label made of any other metal sheet than the iron sheet is soresistant against contamination or staining that even when the labelsurface is stained with dirt or the like, it can be washed with water toremove such dirt. However, in case the label is made of an iron sheet,it will be rusty and thus corroded. Particularly, any iron-sheet barcode label is not suitably usable in a place where the atmosphere isvery salty.

In the head having the structure shown in FIG. 2, since the bonding wire208 is bonded to the electrode 205 on the substrate (semiconductorsubstrate) of the MR device 206 by using an ultrasonic bonder or thelike, an air gap d (about 0.3 mm) must be provided under these elements.This air gap causes the strength of the magnetic lines of force producedby the engraved recesses, that is to be detected by the MR device, to beextremely small. In other words, the MR device has only a lowsensitivity to the magnetic lines of force formed by the bar coderecesses. When the head is off the bar code label, the sensitivity ofthe MR device is found to be very low. For example, when the head isabout 0.1 mm off the label surface in relation to a pattern of recessesof a minimum of 0.5 mm, the head can hardly read the code represented bythe recess pattern.

In the bar code reader having a magnetic sensor of a structure shown inFIG. 3, since the magnetic resistance film 217 inside the reader is solarge as to extend fully across one engraved recess, so the changes ofmagnetic field in opposite directions at the right and left recess edgescancels the magnetic resistance change of the MR device Thus, thisreader cannot read any high resolution engraved bar code composed ofnarrow recesses For example, a common MR device of 0.5 to 0.6 mm inlength and width should preferably be inclined 45 deg. with respect tothe length of the recesses to apply a biasing magnetic fieldlongitudinally of the recesses in order to read the bar code with a highsensitivity. In this case, however, the width of the MR device will beabout 0.7 mm to 0.85 mm and thus it is apparent that the MR devicecannot read any engraved recess of 0.5 mm in minimum width. Also even ifa bar code reading head is constructed with the MR device not inclined45 deg. (the biasing magnetic field may be applied from a directioninclined 45 deg.) but directed longitudinally of the engraved recessesat the sacrifice of the sensitivity to some extent, any common magneticsensor element having a large width fitted in the head cannot read ahigh resolution (namely, narrow) bar code recess pattern.

SUMMARY OF THE INVENTION

The present invention has an object to overcome the abovementioneddrawbacks of the conventional techniques by providing a bar code labelwhich does not rust and which can positively carry and preserveinformation for a long term.

Also the present invention has another object to provide a bar codereader by which anybody can easily read the bar code label with littlepossibility of error.

Further the present invention has yet another object to provide a barcode reader which can read the bar code label with a high sensitivityeven if not in complete contact with the label surface.

The present invention has a further object to provide a bar code readerfor a high resolution bar code label.

According to a first aspect of the present invention, the bar code labelcomprises a base having provided on the top surface thereof a recordingarea in which recesses are engraved each in a predetermined shapecorresponding to information to be recorded the base being coated with anonmagnetic material such as plastic, nickel or the like.

According to a second aspect of the present invention, the bar codelabel is made of a magnetic material in which recesses are engraved eachin a predetermined shape corresponding to information to be recorded,the magnetic material being coated with a nonmagnetic material to renderthe recesses invisible

According to a third aspect of the present invention, the bar code labelhas a record area in which narrower recesses are engraved deeper.

According to a fourth aspect of the present invention, the bar codereader is an apparatus to read a bar code label on which codedinformation is recorded and recognize the code thereon, the apparatuscomprising a head having a reading means, and an elongated main bodyinstalled pivotably and movably to the head.

According to a fifth aspect of the present invention, the bar codereader is provided, in the main body thereof, with a printed circuitboard on which electrical elements are mounted which form a circuitsupplied with a signal from a reading means and which processes it in apredetermined manner, and a shielding means which prevents magneticinterference from taking place between the electrical elements and theexterior of the main body and noise, due to an electric field coupling,from coming in.

According to a sixth aspect of the present invention, the bar codereader comprises a permanent magnet, an MR device formed integrally withthe permanent magnet, a head housing the permanent magnet and MR device,an internal lead wire, a resin film, an input wire of the MR device, andan external lead wire, the head comprising an open casing having a cutat the front end thereof, the internal lead wire facing the front end ofthe head and fixed by being fitted in the cut of the head, a printedcircuit board on which the MR device is mounted being fixed in theopening of the head and electrically connected to the internal lead wireby means of a projection, the external lead wire being passed throughthe head bottom and spot-joined to the internal lead wire, the permanentmagnet being supported at the head bottom and fixed in the head, and theresin film being so formed as to cover the internal lead wire and fillthe cut in the head and also to be flush at the surface thereof with thehead front end.

According to a seventh aspect of the present invention, the bar codereader comprises an MR device and permanent magnet to read a recesspattern engraved in the form of a bar code in a bar code label, the MRdevice having magnetic resistance films inclined about 45 deg. withrespect to the length of the recesses, parallel to each other andcascade-connected in series to each other, thereby detecting a magneticfield change over the recesses, and the permanent magnet being directedlongitudinally of the bar code recesses and inclined about 45 deg. withrespect to the magnetic resistance films, thereby magnetizing the barcode recesses with a DC magnetic field.

According to an eighth aspect of the present invention, the bar codereader comprises an MR device composed of a printed circuit board andmagnetic resistance films which detect a magnetic field change due to abar code label, the magnetic resistance films being integrally formed onthe circuit board and inclined about 45 deg. with respect to a lateralside of the circuit board, parallel to each other and cascade-connectedin series to each other.

According to a ninth aspect of the present invention, the bar codereader comprises a magnetic sensor, a means for amplifying the outputsignal from the magnetic sensor, means for differentiating the outputsignal from the amplifying means, and a means for comparing the outputsignal from the differentiating means with a reference voltage andcoding the result.

According to a tenth spect of the present invention, the bar code readercomprises a bridge circuit consisting of an MR device and resistors,thus forming the magnetic sensor, amplifying means consisting of adifferential amplification circuit and a noninverted amplificationcircuit connected in series to the output of the bridge circuit, adifferentiation circuit connected to the output of the amplifying means,a comparison circuit connected to the output of the differentiationcircuit, and a signal processing circuit comprising a signal outputcircuit connected to the output of the comparison circuit.

According to an eleventh aspect of the present invention, the bar codereader is one having an MR device as magnetic sensor and in which thebridge circuit consisting of the MR device and resistors and a signalprocessing circuit to process the output signal from the bridge circuitare formed integrally in a signal mold.

According to a twelfth aspect of the present invention, the bar codereader is one having an MR device as a magnetic sensor and in which abridge circuit consisting of the MR device and resistors and a signalprocessing circuit to process the output signal from the bridge circuitare formed as a monolithic IC in a single chip.

These and other objects and advantages of the present invention will bebetter understood from the following description made, by way ofexample, of embodiments of the present invention with reference to thedrawings:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of the essential part of theconventional bar code label;

FIG. 2 is also a schematic illustration showing the construction of thehead of the conventional bar code reader;

FIG. 3 schematically illustrates the construction of the conventionalbar code reader having an MR device;

FIG. 4 is a perspective view of a bar code label according to a firstembodiment of the present invention;

FIG. 5 is a sectional view of a bar code label according to a secondembodiment of the present invention;

FIG. 6 is a sectional view of a bar code label according to a thirdembodiment of the present invention;

FIG. 7 is a sectional view of a bar code reader according to a fourthembodiment of the present invention;

FIG. 8 is a block diagram of the circuitry in the bar code reader shownin FIG. 7;

FIG. 9 is a sectional view taken along the line I--I in FIG. 7;

FIG. 10 is a sectional view, enlarged in scale, of the main body andhead of the bar code reader according to the fourth embodiment of thepresen invention;

FIG. 11 is a sectional view of the connection between the main body andhead in the fourth embodiment;

FIG. 12 is a sectional view of a variant of the connection between themain body and head in the fourth embodiment;

FIG. 13 graphically shows the relation between the sweep time and recesspositions in the bar code label when the latter is read by the bar codereader according to the fourth embodiment of the present invention;

FIGS. 14 to 16 show waveforms of signals delivered from the bridgecircuit, differentiation circuit and comparison circuit, respectively,when the bar code label is read by the bar code reader according to thefourth embodiment of the present invention, the waveforms showing thechanges of the respective signals as time passes;

FIG. 17(a) schematically shows the construction of the head of the barcode reader according to a fifth embodiment of the present invention;

FIG. 17(b) is a perspective view of the pen head in which the head shownin FIG. 17(a) is built;

FIG. 18(a) shows the resistance change characteristics of the MR devicewhen the head sweeps across the bar code label;

FIG. 18(b) shows the positions of the recesses engraved in the bar codelabel which correspond to the magnetic resistance change characteristicsin FIG. 18(a);

FIG. 19(a) is a plan view showing the construction of a bar code readerusing an MR device according to a sixth embodiment of the presentinvention;

FIG. 19(b) is a sectional view taken along the line A--A' in FIG. 19(a);

FIG. 20 is a plan view showing the construction of an MR deviceaccording to a seventh embodiment of the present invention;

FIG. 21 is a block diagram showing the construction of a bar code readeraccording to an eighth embodiment of the present invention;

FIG. 22 is a block diagram of an internal circuit composing the magneticsensor in the bar code reader according to the eighth embodiment of thepresent invention; and

FIGS. 23(a) to (c) show signal waveforms, respectively, at variouspoints of the magnetic sensor according to the eighth embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 4 shows a bar code label according to the present invention, thisengraved bar code label comprising a base 1 having a protective film 2formed on the outer surface thereof.

The base 1 is a square sheet made of a material such as iron or thelike, the sheet having the top and bottom surfaces thereof each machinedto a mirror surface to minimize surface irregularity. The base 1 hasformed on the top surface thereof a record area 3 carrying, foridentification, a variety of information on, for example, the name of aunit or force to which a soldier belongs or the proprietor, serialnumber or the like of an outdoor installation such as a constructionmachine, vehicle, gas cylinder, machine part, steel tower or the like.The record area 3 consists of engraved recesses different in width fromeach other corresponding to various information. In this firstembodiment, the recesses are formed by etching or punching.

The protective film 2 is provided for long term protection of the recordarea 3 from erosion and corrosion and it is selected from among plastic,nickel, lead (Pb) or tin (Sn). Stainless material such as plastic,nickel or the like is applied as a thin film on the entire surface ofthe base 1. A film of lead or tin is applied by plating the entiresurface of the base 1 Thus, according to this embodiment, the protectivefilm 2 is applied on the entire surface of the base 1 easily and withlow cost.

Next, the second embodiment of the present invention will be discussedbelow:

FIG. 5 shows another bar code label according to the present invention.This engraved bar code label comprises a base 4 in the form of a sheetof a ferromagnet:c material such as iron (Fe), cobalt (Co), nickel (Ni)or the like and on which a record area 5 is provided which consists ofrecesses different in width from each other and which are engraved witha predetermined spacing from one to another recess, and a nonmagneticfilm 6 so molded in the record are 5 of the base 4 as to completely fillthe recesses.

Similar to the base according to the first embodiment discussed above,the base 4 in this second embodiment has the top and bottom surfacesthereof machined with a high precision to a mirror surface to preventany reading error from taking place.

The record area 5 in this embodiment has engraved in the top surface ofthe base 4 recesses each having a predetermined width corresponding toinformation to be recorded, spaced predetermined distances fromadjoining ones and engraved to a predetermined depth d. When a magneticfield is applied to this record area 5 from outside by a magnet or thelike, the magnetic lines of force are concentrated laterally of therecesses, resulting in a distortion of the distribution of the magneticlines of force. By detecting the components of the distribution in thedirection of the distribution width, signals corresponding to the edgesof the recesses are produced, and further by decoding the signals, theoriginal record pattern can be recognized and reproduced.

The nonmagnetic film 6 is molded of a nonmagnetic m;aterial such asplastic or the like to a predetermined thickness onto the record area 5.

The third embodiment of the present invention will be discussed below:

FIG. 6 shows yet another engraved bar code label according to theinvention, in which the depth d₁ of a recess 7 of smaller width W₁ islarger than the depth d₂ of another recess 7 of larger width W₂, namely,d₁ >d₂.

Because the depth d₂ is smaller than the depth d₁, the magnetic fieldnear the wide recess is prevented from being highly distorted, whichleads to less distortion of the magnetic field on the adjoining narrowrecess.

Therefore, according to this third embodiment, the recess depth ischanged inversely to the recess width; thus, the output waveformcorresponding to each recess 7 is less distorted during the informationreading and thus a high information density, namely, high resolution barcode label, can be read accurately.

In the aforementioned bar code labels according to the first to thirdembodiments of the present invention, the record area consists ofbar-like recesses, but the present invention is not limited to thisshape of recess and the recesses may be formed in the shape of, forexample, a predetermined symbol, character or the like.

FIG. 7 shows a bar code reader according to a fourth embodiment of thepresent invention. The bar code reader comprises a main body 9 and ahead 10 to magnetically read a bar code label 8 on which information ismagnetically recorded, for recognition of the information.

Note that the bar code label 8 is the same as the bar code labelaccording to the aforementioned first embodiment of the presentinvention. That is, this bar code label 8 has a record area consistingof recesses engraved in the magnetic base, each recess having apredetermined width corresponding to a piece of information to berecorded, and the recesses being spaced predetermined distances fromeach other. The bar code label 8, in use, is securely attached to thebottom of a recessed portion 11a or the like of a particular item to belabelled, for example, equipment 11 which is used outdoors.

The main body 9 comprises a long cylinder in which there is provided aprinted circuit board 12 having mounted thereon electrical elements (notshown) forming together a circuit to process a signal in a predeterminedmanner and a shielding means 13 for preventing magnetic interferencebetween the electrical elements and the exterior of the main body 9 aswell as noise due to electric field coupling, and the main body 9 isconnected to a decoder (not shown) outside the main body 9 by means of acable 14. The circuit board 12 has formed thereon a signal processingcircuit, of which the circuit configuration will be seen from FIG. 8,consisting of an amplification circuit 15, differentiation circuit 16,comparison circuit 17 and a polarity inversion circuit 18. Theamplification circuit 15 amplifies an electric signal resulting from amagnetic resistance change caused by the MR device which will bediscussed later. In this embodiment, the amplification circuit 15 iscomposed of two stages of amplifiers each made of a linear IC and hasthe input thereof connected to a bridge circuit of which the MR deviceis provided and the output thereof connected to the input of thedifferentiation circuit 16. In this differentiation circuit 16, theelectric signal amplified by the amplification circuit I5 is wave-shapedin a predetermined manner for identification of the recess width in therecord area on the bar code label 8. The differentiation circuit 16 hasthe input thereof connected to the output of the amplification circuit15 and the output thereof connected to the input of the comparisoncircuit 17. The comparison circuit 17 responds to the width of eachrecess in the record area which is identified by the differentiationcircuit 16 and converts an analog signal of a predetermined waveforminto a digital signal of a rectangular waveform or the like. In thisembodiment, a linear IC is used as the comparator, and the comparisoncircuit 17 has the input thereof connected to the output of thedifferentiation circuit 16 and the output thereof connected to the inputof the polarity inversion circuit 18. The polarity inversion circuit 18returns to the initial state the phase of the output waveform shifted 90deg. during wave-shaping in the differentiation circuit 16, namely, tothe phase corresponding to the recesses in the record area on the barcode label. This inversion circuit I8 consists of two stages oftransistors, of which the input is connected to the output of thecomparison circuit 17 while the output is connected to the input of thedecoder circuit (not shown) outside the main unit 9. The elongatedcircuit board 12 having mounted thereon various electrical elementsforming these circuits is fitted at the lower end thereof in a recess19a formed on the top of a retainer 19 projecting upward from the bottomof a housing 19 as shown in FIG. 9, and at the upper end thereof isclosely fitted in a recess formed in a retainer 21 which is urgeddownwardly by the resilience of a spring 20 as shown in FIG. 7. Itshould be noted that these circuits may be formed each by a combinationof electrical elements such as individual ICs, resistors, capacitors andso forth disposed on the circuit board, and also that these elements maybe combined into a hybrid IC or monolithic IC mounted on the circuitboard.

The head 10 is connected pivotably and movably to the main body 9, andcomposed of a base 23 connected to the bottom of the housing 9a of themain body 9 by means of a pivoting/moving mechanism 22, a reading means24 provided on the base 23, and a skirt 32 as shown in FIG. 10. Thepivoting/moving mechanism 22 is provided to smoothly scan the head 10for reading the bar code label 8 and to freely pivot and vertically movethe head 10 in relation to the housing 9a of the main body 9. To thisend, the pivoting/moving mechanism 22 comprises, as shown in FIG. 11, acoupling member 25 having an elongated hole 25a and secured to thebottom of the housing 9a, a bracket 27 pivotably supporting a pivotshaft 26 through the elongated hole 25a in the coupling member 25 andprovided upright on the base 23, and a spring 29 applying a resilientforce toward the pivot shaft 26 in the elongated hole 25a by means of apusher 28 (as seen from FIG. Although a resilient force is applied tothe pivot shaft 26 by the coil spring 29 in this embodiment, this isjust an example. The present invention is not limited to this embodimentbut, for example, a plurality of generally inverted V-shaped leafsprings 30 may be used in place of the coil spring, as shown in FIG. 12.As the reading means 24, an MR device is employed. In this embodiment,an MR device and predetermined resistors are combined to form a bridgecircuit. The output of the bridge circuit is connected to the input ofthe amplification circuit 15 provided on the circuit board 12 by meansof an interconnecting cord passed through a hole 9b at the bottom of thehousing 9a. Note that the MR device is so designed that the internalresistance changes corresponding to the size of external magnetic fieldand it is made of a silicon compound semiconductor, ferromagnetic film(metal) or the like.

Next, how each of the circuits involved in this embodiment functionswill be discussed below:

Assume that the bar code reader according to this embodiment is used toscan an engraved bar code label 8 having, for example, a shape(thickness) as shown in FIG. 13. The bridge circuit comprising the MRdevice delivers a signal of a waveform of which each of the extremevalues corresponds to a respective recess boundary as seen from FIG. 14.

Next, this output signal from the bridge circuit is amplified by theamplification circuit and then supplied to the differentiation circuit16 which in turn will deliver to the comparison circuit 17 a signal of awaveform phase-shifted from the output waveform from the bridge circuitand precisely corresponding to the recesses on the bar code label 8 asshown in FIG. 15.

Then the comparison circuit 17 delivers a coded digital signalcorresponding to the shape of the recesses in the bar code label 8 asshown in FIG. 16.

Hence, in this embodiment, even if the bar code label 8 is secured in,for example, a narrow recessed portion 11a as shown in FIG. 7, it can bepositively scanned and read by the head by pivoting the main body 9.

FIG. 17(a) shows the construction of the bar code reader according to afifth embodiment of the present invention, and FIG. 17(b) shows theshapes of a main body 33 and head 34 of this bar code reader.

The bar code reader according to the present invention has a penhead-type structure to sweep the bar code label 201 (basically the oneshown in FIG. 1) and read the code thereon. The head at the tip of thereader is built in a head frame 35 as shown in FIG. 17(a). The headframe 35 is an open casing having a cut 35a formed at the end thereof.According to the present invention, a permanent magnet 36 is supportedon the bottom 35b within the head frame 35 and a printed circuit boardon which an MR device 37 is formed by predetermined IC manufacturingprocess is supported on an internal lead wire 38 in a hole 35c andfacing the end of the head frame 35.

The internal lead wire 38 is formed on a resin film 39 by patterning.The resin film 39 is fitted in the cut 35a and the surface thereof is soshaped as to be flush with the end of the head frame 35. The internallead wire 38 and circuit board 40 are joined to each other by means of aprojection 41. The projection 41 is previously attached to. the internallead wire 38 and connected, by being pressed from the resin film side bymeans of a bonding tool, to an input wire 37' of the MR device 37 laidon the circuit board 40.

The input wire 37' is made of Au or the like while the internal leadwire 38 is of Cu or the like.

The resin film 39, internal lead wire 38 and circuit board 40 are coatedwith a resin film 42 for protection from the environment and also forprevention of their separation. Passing through the bottom 35b of thehead frame 35 are circular or square throughholes 43', 44 and 44'through which resin for forming a resin coating 45 is passed to securethe resin film 39 and internal lead wire 38 to the head frame 35.

It should be noted that the permanent magnet 36 is mechanically fixed tothe head frame 35 by means of the resin coating 45.

An external lead wire 46 through which a current is supplied to the MRdevice 37 which detects a resistance change is passed through the bottom35b and solder-joined to the internal lead wire 38.

In the head 34 of such construction, the resin film 39, internal leadwire 38 and projection 41 are about 0.1 mm, 0.05 mm and 0.01 mm thick,respectively. The gap between the surface of the resin film 39, namely,the end of the detector (end of the head frame), and the surface of theMR device (circuit board surface) is about 0.15 mm. This gap size isnearly half that in the conventional reader in which a bonding wire isused. Because of the fact that magnetic field strength attenuate inproportion to one/square or one/cube of distance, the sensitivity ofdetection is four times higher than in the conventional reader. FIG.18(a) shows the magnetic resistance change when the reader is sweptacross a bar code label 50 (with minimum recess pattern of 0.5 mm) madeof a metal. FIG. 18(b) shows the relation between the recesses engravedon the bar code label 50 and the magnetic resistance change. Theresistance change characteristic α is one obtained when the bar codereader according to the present invention was used while thecharacteristic β is one obtained by using the conventional reader. Inthe reader according to the present invention, the magnetic resistancechanges more greatly than in the bar code reader of the conventionalstructure. Even when the head 34 is swept at a height of about 0.1 to0.2 mm above the top surface of the bar code label, the code could beaccurately read.

Having a high sensitivity as mentioned above, the bar code readeraccording to the present invention can read a engraved record in a barcode label even when the latter is somewhat stained with an oil, dust orminute metal pieces.

Since being able to tolerate fluctuations of sensitivity equivalent todistancing the head from the top surfac of the bar code labelapproximately 0.1 to 0.2 mm, the bar code reader according to thepresent invention is highly reliable.

Next, the MR device according to the sixth embodiment of the presentinvention and a bar code reader using the MR device will be discussedbelow:

As shown in FIGS. 19(a) and 19(b), the MR device according to thepresent invention is composed of magnetic resistance films 48 formed onthe surface of the circuit board 47 which is made of Si, glass or thelike, and an electrode 49 of Au or the like through which a current issupplied to the magnetic resistance films 48. The ends of the magneticresistance films 48 are in vertical alignment and the magneticresistance films are parallel to each other and inclined about 45 deg.with respect to the lateral sides of the circuit board 47, and they arecascade-connected in series to each other by means of electricallyconductive films 48a. Thus, since the width, i.e., the dimension alignedwith the width of the recesses, of the array of magnetic resistancefilms 48 which detect a magnetic field change is less than thelongitudinal length of the array, namely, about 70% thereof, themagnetic resistance films 48 will not extend on both the opposite sidesof engraved recesses 51 in the same bar code label 50 as in theaforementioned fifth embodiment, so the bar code label 50 can be readeven if the engraved recesses 51 in the bar code label 50 form a highdensity pattern. When the array of magnetic resistance films 48 is, forexample, 0.5 to 0.6 mm long, its width is only 0.35 to 0.42 mm. Namely,it is possible to read bar code recesses each of 0.5 mm in width by thehead according to this embodiment. Further, in case the bar code recesswidth is made smaller, high resolution bar code reading can be assuredby shortening the length of each of the magnetic resistance films 48while increasing the number of the films 48 verticallycascade-connected. In the conventional pattern of magnetic resistancefilms, however, since the ends of the respective films will overlap oneach other even though the films are cascade-connected, no high densitybar code pattern can be read. Therefore, the structure of the headaccording to the present invention is advantageous for reading a highresolution pattern.

With the arrangement of the head according to the present invention, thelarger the number of magnetic resistance films, the higher thesensitivity of detection of magnetic resistance change due to the barcode recesses. Thus, the present invention is also advantageous forproviding a highly sensitive reader.

In the bar code reader according to the present invention, a permanentmagnet 52 used in conjunction with the aforementioned MR device ispositioned as will be discussed below. Namely, for biasing the magneticresistance films 48 of the MR device, the permanent magnet 52 is sodisposed that the poles 52a and 52b thereof are shifted 45 deg. withrespect to the length of the array of films 48. As shown in FIG. 19(a),the permanent magnet 52 is mounted on the circuit board 47 of the MRdevice in such a manner that the poles 52a and 52b are positionedvertically, that is, on an axis parallel to the length of the recesses51. Thus, the MR device can be set in the most sensitive, optimum biasedstate. At this time, the magnetic resistance films 48 are verticallybiased. When the head 53 using the permanent magnet 52 and the MR devicein conjunction with each other is swept in relation to the recesses 51on the bar code label 50 with the lateral side 47a of the MR devicecircuit board and that of the permanent magnet 52 being nearly flushwith the length of the recesses 51 as shown in FIGS. 19(a) and 19(b),the magnetic field changes due to the recess edges are applied in thesweeping direction so that the MR device will cause the magnetic fieldchanges to incline in a direction within a range of +/-45 deg., and thusthe magnetic field will fully change within a linear magnetic resistancechange range of the MR device. Namely, the bar code can be read in awide dynamic range. Thus, even if the head is swept somewhat above thebar code label, a stablc reading of the label can be assured since theresulting voltage signal amplitude corresponds to a relatively largemagnetic resistance change.

Namely, the bar code reader according to the present invention is highlyreliable.

FIG. 20 shows the structure of the MR device according to the seventhembodiment of the present invention.

According to this seventh embodiment, the lower one (55) ofcurrent-supplying electrodes 55 and 55 extends on a printed circuitboard 54 from one lateral side 54a of the circuit board toward the otherlateral side 54a, magnetic resistance films 56 are disposed at aninclination of 45 deg., the lowest one of the films 56 extends to and isconnected to the lower electrode 55, and the magnetic resistance films56 are cascade-connected to each other with the electrode 55 interposedbetween adjoining films 56. Thus, since the current is supplied only inone direction to the magnetic resistance films 56, no resistance changedue to a magnetic field depending upon the direction of the current willoccur, so that a stable detection of magnetic field change is assured.The operating principle and other effects of this embodiment are quitethe same as those in the aforementioned sixth embodiment.

Next, the eighth embodiment of the present invention will be discussedbelow:

FIG. 21 is a block diagram of the bar code reader according to theeighth embodiment of the present invention. As seen from FIG. 21, thebar code reader according to this embodiment comprises a magnetic sensor60 having an MR device as an essential element, an amplifying means 61to amplify an analog voltage waveform output from the magnetic sensor60, a differentiating means 62 to detect a start signal of the amplifiedanalog voltage waveform and also to differentiate this analog voltagewaveform, and a coding means 63 to shape the differentiated signal andextract a code signal therefrom.

FIG. 22 is a block diagram showing the component circuits of the barcode reader according to the eighth embodiment of the present invention.

As shown in FIG. 22, an output voltage from a bridge circuit 68consisting of an MR device 64 and resistors 65, 66 and 67 and thusforming the magnetic sensor is supplied to a differential amplificationcircuit 69 which forms, together with a noninverted amplificationcircuit 70, the above-mentioned amplifying means 61.

The differential amplification circuit 69 is composed of a linear IC 73having a negative feedback circuit consisting of a capacitor 71 andresistor 72, and three input resistors 74, 75 and 76. This differentialamplification circuit 69 amplifies a differential voltage of a signalsupplied to the negative and positive terminals of the linear IC 73 fromthe bridge circuit 68 and delivers it to the noninverted amplificationcircuit 70. This circuit 70 consists of a linear IC 79 having a negativefeedback circuit composed of a capacitor 77 and resistor 78, and aninput resistor 80. The output signal from this noninverted amplificationcircuit 70 is supplied as input to a differentiation circuit 81 formingthe differentiating means 62.

The differentiation circuit 81 consists of a linear IC 84 having anegative feedback circuit composed of a capacitor 82 and resistor 83, aseries circuit composed of a resistor 85 and capacitor 86 connected tothe negative terminal of the linear IC 84, and a reference voltagesource connected to the positive terminal. This differentiation circuit81 delivers to a comparison circuit 87 forming the coding means 63 anoutput signal phase-shifted 90 deg. with respect to the input signal.

The comparison oirouit B7 oonsists of a linear IC 90 having a positivefeedback circuit formed by a resistor 89, a resistor 91 connected to thenegative terminal of the linear IC 90, and a reference voltage sourceconnected to the positive terminal of the linear IC 90. This comparisoncircuit 87 compares an input signal supplied to the negative terminalwith the reference voltage applied to the positive terminal and deliversan output pulse "H" or "L" to a signal output circuit 88.

The signal output circuit 88 is formed by two transistors 92 and 93 soconnected as to turn on and off in such a manner that when one of thetransistors turns on, the other turns off and when the one turns off,the other turns on. More particularly, when the transistor 92 is turnedon by a pulse "H" supplied to the base terminal of the transistor 92through a resistor 94, a current flows from the collector of thetransistor 92 to the emitter thereof through a resistor 95 connected tothe connector terminal thereof. As a result, the base voltage of thetransistor 93 connected to the collector terminal of the transistor 92through a resistor 96 drops, so that the transistor 93 is turned off.Likewise, when the pulse supplied from the comparator circuit 87 is "L",the transistor 92 is turned off while the transistor 93 is turned on.Thus, the output pulse from the comparison circuit 87 is delivered as apulse of an inverted polarity at the signal output circuit 88.

The functional sequence of the magnetic sensor 60 will be discussed withreference to FIG. 23.

FIGS. 23(a), 23(b) and 23(c) show the signal waveforms at variousportions of the magnetic sensor 60; in particular, FIG. 23(a) shows thewaveform of the output voltage from the bridge circuit 68, correspondingto the shape of the engraved magnetic recesses, FIG. 23(b) shows thewaveform of the output voltage from the differentiation circuit 82, andFIG. 23(c) shows the coded pulse group, which is the output from thecomparison circuit 87.

When the bar code-like magnetic recesses engraved in the bar code labelare magnetized by the magnetic field source such as the permanent magnetor the like provided in the bar code reader, the magnetic field ischanged by the engraved recesses (the magnetic field becomes the maximumand minimum at the recess edges) and the change amount appears as achange of the output voltage of the bridge circuit 68.

The output signal resulting from the amplification of the output fromthe bridge circuit 68 is further amplified, then phaseconverted andappears as a change in duration of the output pulse delivered from thecomparison circuit 87.

More particularly, the recess width is proport-ional to the output pulsewidth. So, the bar code reader using the magnetic sensor 60 according tothe present invention can be used to read the bar code formed by aplurality of recesses different in width and spacing between them,namely, the information recorded in the record area.

It is apparent that the magnetic sensor thus constructed is different instructure from the conventional ones used in speedometers, printers andthe like. Provided with an extreme value detecting means, the magneticsensor according to the present invention can magnetically detect andreproduce a pattern on a magnetic bar code label with a higheffectiveness and efficiency.

Thus, even if stained with dirt or the like or somewhat impaired, thepattern on the bar code label (metallic) can be read accurately.

Furthermore, the magnetic sensor may be made in the form of a singlemold or a single chip. Since the mold or chip are very small devices, ahandy bar code reader can be designed.

As having been discussed in the foregoing, a bar code label according tothe present invention has recesses engraved in a record area on the barcode label. Even with any staining, sunlight or the like, the recordarea cannot be lost. Therefore, information can be positively recordedon the bar code label, particularly for outdoor use for a long term.

A magnetic engraved bar code label according to the present inventionpermits recording information on the magnetic material with a width andspacing corresponding to the information based on the fact that when anexternal magnetic field is applied from a ferromagnetic material such asa magnet or the like to the record area made of a magnetic material, thedistribution of magnetic lines produced by the respective in the recordare is changed at the recess edges.

Engraved bar code labels according to the present invention are made ofa ferromagnetic material (metal) coated with a resin or the like. Soeven if stained or somewhat impaired, the label can still be used.Namely, it can be suitably used in an environment such as outdoors,factories or the like where the label is likely to be stained.

A bar code reader according to the present invention may be soconstructed that the head is rotatably coupled to the main body. Thus,the user can take a convenient position when reading the bar code label,and just by pressing the main body with a predetermined force, the headis moved toward the label surface and can be positively put into closecontact with the label surface, whereby any reading error can beprevented. Therefore, the bar code reader according to the presentinvention is highly reliable.

Also, a bar code reader according to the present invention may use astructure in which the MR device and lead wires are connected to eachother by means of a projection, which can surely provide a highlyreliable bar code reading system. Even if stained with oil, dust or mud,this reader can still be used normally. Thus, it can be used effectivelyin any desired environment, such as outdoors, factories or the like.

A bar code reader according to the present invention may use an MRdevice consisting of obliquely extending, cascade-connected magneticresistance films, permitting reading a high density bar code patternwith a high sensitivity. By adopting a bar code detector in which apermanent magnet is so disposed as to provide a biasing from a directionshifted about 45 deg. with respect to the length of the MR device, theMR device can be operated in a wide dynamic range, thereby permitting ahigh sensitivity reading. Namely, the bar code reader of the presentinvention provides for a highly reliable bar code reading system.

A bar code reader according to the present invention incorporates amagnetic sensor and thus provides for a bar code reading system which ishighly durable, not easily affected by the operating environment, hardlyinfluenced by staining or impaired during storage or transportation andwhich is easy to handle in reading information from bar codes or thelike.

A bar code reader of the present invention may have the internal circuitformed in an integral mold or a single-chip monolithic IC, whereby thereader not only is more reliable but also can be manufactured morecompact and with lower costs.

What is claimed is:
 1. A bar code label comprising a base havingprovided on the top surface thereof a record area in which recesses areengraved each in a predetermined shape corresponding to an informationto be recorded, said base, including the recesses in said base, beingcoated and in contact with a nonmagnetic material.
 2. A bar code labelcomprising a base made of a magnetic material in which recesses areengraved each in a predetermined shape corresponding to an informationto be recorded, said base being coated with a non-magnetic material to asufficient depth that the recesses are not visable.
 3. A bar code labelcomprising a base made of a magnetic material in which recesses areengraved each in a predetermined shape corresponding to an informationto be recorded, said base being coated with a nonmagnetic material to asufficient depth that the recesses are not visible, said base having arecord area with at least first and second recesses, said second recessbeing narrower and engraved deeper than said first recess.